Remote Operations
How to Use Commands 5
5-25
How to Use Commands
Communications between the controller and the Calibrator consists of commands,
queries, and interface messages. Although the commands are based on the 488.2
standard, they can be used on either the IEEE-488 or RS-232 interface, except for a few
specialized RS-232 commands described in “Commands for RS-232 Only.” (For more
information on command structures, see the IEEE 488.2 standard.)
Refer to Chapter 6, “Remote Commands” when you require additional information about
command references used this chapter.
All commands and units may be entered in UPPER or lower case.
There are four specific remote control configurations that use commands, queries and
interface messages: IEEE-488, RS-232 Terminal Mode, RS-232 Computer Mode, and
RS-232 Pass-Through Mode. (Setting up and testing each mode is discussed earlier in
this chapter.)
IEEE-488 Mode The IEEE-488 mode is used when the Calibrator is operated by
computer program. In this mode, requested information is returned by query, and
interface messages are queued and returned by command.
RS-232 Terminal Mode The RS-232 terminal mode is an interactive mode where an
operator inputs commands, with immediate returns for requested information (queries)
and interface messages.
RS-232 Computer Mode The RS-232 computer mode is used when the Calibrator is
operated by computer program. In this mode, requested information is returned by query,
and interface messages are queued and returned by command.
RS-232 Pass-Through Mode The RS-232 pass-through mode is used to pass commands
from the PC to a UUT, but via the Calibrator. This configuration is used when the UUT
has an RS-232 port. Commands are sent to the UUT by using the UUT_SEND command,
returns use the UUT_RECV? query, and UUT_FLUSH clears the UUT receive buffer in
the Calibrator.
Types of Commands
The commands for the Calibrator can be grouped into one or more categories, depending
on how they function. Each category is described below.
Device-Dependent Commands
Device-dependent commands are unique to the Calibrator. An example of a device-
dependent command is,
OUT 100 V, 1 A, 60 HZ
Instructing the Calibrator to source 100 watts of ac power.
Common Commands
Common commands are defined by the IEEE 488.2 standard and are common to most
bus devices. Common commands always begin with an * character. Common commands
are available whether you are using the IEEE-488 or RS-232 interface for remote control.
An example of a common command is,
*IDN?
instructing the Calibrator to return the instrument identification string.
Query Commands
Query commands request information, which is returned as the command executes, or
placed in a buffer until requested. An example of a query, which always ends with a
question mark, is,
RANGE?
returning the Calibrator primary and secondary outputs.
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